While recent clinical trials have prompted an important reevaluation of estrogen therapy, the majority of evidence suggests that the post-menopausal heightened risk of mortality from heart disease may be attenuated by estrogen, resulting in a 40-50% decrease in the incidence of heart disease. Nonetheless, given the potential for accelerated disease progression associated with estrogen replacement in some women, investigating alternative interventions for protecting against the post-menopausal increase in mortality from heart disease is of great interest. One potential alternative therapy for decreasing the risk of mortality from ischemic heart disease is endurance exercise. It is well established that exercise improves tolerance to myocardial ischemia and reperfusion. Endurance exercise improves contractile performance and attenuates infarction size. The mechanism(s) to explain the cardioprotective effect of exercise remain elusive. Estrogen and exercise appear to exert similar cardioprotective effects and estrogen has been shown to do so via protection of both cardiac myocytes and vascular endothelial cells. The proposed research will further our understanding of mechanisms of exercise and estrogen-induced cardioprotection by addressing: (1) whether the protective effects of exercise are targeted at cardiomyocytes versus vascular endothelium, (2) if exercise protects cardiomyocytes and endothelial cells against apoptotic versus necrotic cell death, (3) whether exercise-mediated protection is dependent on estrogen (i.e., whether exercise protects similarly pre- and post-menopause and whether exercise-induced protection is gender-dependent), and (4) if exercise and estrogen facilitate cardioprotection via NFkB-mediated signaling. These aims will be addressed using cardiac myocytes and aortic endothelial cells isolated from exercised rats, employing specific pharmacological inhibitors. These studies will improve our understanding of the mechanisms of exercise-induced cytoprotection, perhaps leading to alternative therapies for decreasing mortality from heart disease.